Conventional systems that detect analytes have limited flexibility and are unable to accurately and repeatably analyze a variety of analytes in a range of volumes and under a range of flow rates. Some inflexible analyte detection systems enable sample addition at only a single point in time and/or location in the analysis process. Thus, conventional analyte detection systems are limited to use in certain applications. Further, systems that detect analytes (e.g., biological agents) are generally large in size, precluding system use in certain applications, for example, in the field. In addition, systems that detect analytes are limited, because analyte sample contamination requires the entire system to be sterilized by, for example, autoclaving after each detection cycle.